Adobe Flex systemManager_removedHandler() Error

Adobe Flex hasn't still solved the problem on their error...

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mx.managers::HistoryManager$/unregister()
at mx.containers::ViewStack/private::systemManager_removedHandler()
at flash.display::DisplayObjectContainer/removeChild()
at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::$removeChild()
at mx.core::Container/removeChild()
at mx.modules::ModuleLoader/set url()
at mainscreenpage/loadmodules()
at tmscanvas::tmsside/__btnSearch0_click()
at [mouseEvent]

This occurs when you have used the components like accordion, viewstack and other such component of the same category.

Fortunantely, there is one solution to stop this bug. Add the following script to the main mxml of your application. Main mxml means the first mxml to load when you run the project.

import mx.managers.DragManager;
import mx.validators.DateValidator;
import mx.containers.TabNavigator;
private var dm:DragManager;
private var dv:DateValidator;
private var tn:TabNavigator;

That's it! Solved! But I hope Adobe would fix this problem on Flex.

Adobe Flex systemManager_removedHandler() Error